1. Field of the Invention
The present invention relates in general to automatic washing machines using low frequency vibration in clothes washing and, more particularly, to an improved structure in such washing machines for saving the input energy during generation of resonance phenomena in the multi-phase washing medium for clothes washing.
2. Description of the Prior Art
In a typical pulsator type washing machine, a pulsator is provided in the washing tub. In clothes washing using the above pulsator type washing machine, the pulsator is alternately rotated in opposed directions by forward and reversed rotational forces of a drive motor under the control of a motor clutch, thus to generate a heart type current or a scroll type current in the multi-phase washing medium in the washing tub. Here, the multi-phase washing medium consists of water, detergent and air. In the above clothes washing, the pulsator type washing machine achieves a mechanical washing effect by bending, stretching and rubbing the clothes using the shearing force of the washing medium. This mechanical washing effect cooperates with a chemical washing effect caused by the detergent in the washing medium, thus to achieve the desired washing effect.
However, the above pulsator type washing machine has the following problems.
First, the typical pulsator type washing machine is apt to cause twisting and entangling of the clothes in the washing tub because of agitation caused by opposed directional rotations of the pulsator. In this regard, the washing machine may cause both damage of clothes and deterioration of the washing effect.
Second, the washing machine is reduced in the detergent solubility of the current and often causes the washed clothes to be stuck with detergent remnants. In this regard, the washing machine should waste large amount of water and lengthen the washing time. Furthermore, the detergent remnants sticking to the washed clothes have a bad effect to the skin.
In order to overcome the above problems of the typical pulsator type washing machine, there has been proposed a low frequency vibration type washing machine using a low frequency vibration in the clothes washing. In clothes washing using the typical low frequency vibration type washing machine, a low frequency oscillating disc placed in the washing tub generates a specified low frequency vibration which causes the resonance phenomena in the multi-phase washing medium in the washing tub. The level of low frequency is specified in accordance with shape of the washing tub, shape of the oscillating disc and mixing ratio of the multi-phase washing medium.
In the above washing machine, the desired mechanical washing effect is achieved by the micro air bulbs generated by cavitation of the oscillating disc or nonlinear vibration. Both the cavitation or the nonlinear vibration is generated in the multi-phase medium at the same time of generation of the resonance phenomena. The mechanical washing effect caused by the cavitation or the nonlinear vibration cooperates with a chemical washing effect caused by the detergent in the washing medium, thus to achieve the desired washing effect.
With reference to FIG. 1, there is shown a typical automatic washing machine using the low frequency vibration. The washing machine generally comprises a washing tub 1a, receiving multi-phase washing medium therein, and a low frequency oscillating disc 4a causing the resonance phenomena in the washing medium. The oscillating disc 4a is placed in the washing tub 1a and coupled to an actuator 2 through a shaft 3. The shaft 3 transmits the drive force of the actuator 2 to the disc 4a so as to drive this disc 4a. The actuator 2, which is mounted on the outer bottom of the washing tub 1a, is applied with an amplitude signal and a frequency signal from a signal oscillator 7. A signal amplifier 8 is placed on a line between the actuator 2 and the signal oscillator 7 for amplifying and varying the signals generated by the signal oscillator 7.
There is provided a gap between the inner bottom of the washing tub 1a and the disc 4a for allowing the disc 4a to vertically vibrate. A lid 9 is provided in the opening of the washing tub 1 for covering the opening.
In operation of the above washing machine, the low frequency oscillating disc 4a is driven by the actuator 2 in response to signals applied from the signal oscillator 7 to the actuator 2 through the signal amplifier 8. This disc 4a thus oscillates in order to cause the resonance phenomena in the multi-phase washing medium in the washing tub 1a. Here, the desired mechanical washing effect is achieved by the micro air bulbs generated by cavitation of the oscillating disc or nonlinear vibration, which cavitation and nonlinear vibration are generated in the multi-phase medium at the same time of generation of the resonance phenomena. The above mechanical washing effect cooperates with the chemical washing effect caused by the detergent in the washing medium, thus to achieve the desired washing effect as described above.
In the above clothes washing using the low frequency vibration, the signal oscillator 7 makes the oscillating disc 4 oscillating in an oscillation frequency band of 20-250 Hz, an amplitude band of 2-25 mm and a rotational amplitude band of 2.degree.-10.degree.. Here, the signal amplifier 8 amplifies current signals or voltage signals which are to be applied from the signal oscillator to the actuator 2.
It has been noted that the above low frequency vibration type washing machine has the following problems.
First, in the above washing machine, the desired resonance phenomena of the washing medium can not generated by only the stiffness of the fluid in the washing tub. In this regard, the washing machine can not achieve the desired washing effect with minimum input energy.
Second, the clothes may be jammed in the gap between the oscillating disc 4a and the inner bottom of the washing tub 1a. When the clothes are jammed in the gap as described above, the clothes may be damaged and the washing effect of the washing machine will be deteriorated.